ROME , Italy -LRB- CNN -RRB- -- Italian authorities Tuesday arrested two suspects believed to be responsible for the September 18 killing of six African immigrants in Castelvolturno , a small town of 20,000 residents north of Naples .

The army has been deployed in major cities aross Italy since the early summer .

Police also arrested a third man wanted by authorities for belonging to the same clan , but not directly linked to the killings .

The victims were gunned down in a hail of bullets as they stood outside a store selling ethnic goods . The attack sparked a riot by immigrants who complained about `` racism '' but officials suspect a dispute over drug trafficking .

Those arrested , Alessandro Cirillo , Oreste Spagnuolo and Giovanni Letizia , were on the list of the 100 most dangerous men and wanted criminals in Italy .

The arrests were part of a large police operation aimed at cracking down on organized crime in the Campania region and in particular the powerful Casalesi clan belonging to the Neapolitan mafia known as Camorra .

The Casalesi clan and the area where the arrests took place prominently featured in the best seller `` Gomorrah , '' a book written by Roberto Saviano who now lives under constant police protection .

`` This is a great day for the Italian state , '' said Carmelo Casabona , head of the police in Caserta . `` The operation was an immediate , concrete and strong answer to organized crime in this region . ''

Two weeks ago , the Italian interior minister announced the deployment of 400 additional police officers in the area . And the Italian military will deploy 500 troops by Saturday as part of a large operation Italian officials say is aimed at `` reclaiming the control of the territory . ''

`` Our objective is to take the water away from the sharks , '' said Italian Interior Minister Roberto Maroni .

He explained that the additional police officers are already working , while the army 's role will be defined at a key meeting Friday in Caserta .

In the suspects ' home , police found weapons including two AK-47s that investigators say were used to carry out the killings in Castelvolturno , as well as police overalls , one gun and one pump rifle .

Authorities also arrested dozens of other people , including the wife of Francesco Schiavone , aka `` Sandokan , '' the head of the Casalesi clan who was arrested a decade ago and is serving a life-time prison sentence .

As part of the same operation , Italian financial police confiscated 43 companies and 134 apartments spread throughout central and southern Italy belonging to the Casalesi clan , worth more than 100 million euros -LRB- $ 144 million -RRB- .

CNN Producer Flavia Taggiasco contributed to this report .

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Two suspects arrested over killing of six African immigrants in Italy

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Victims were gunned down in a hail of bullets in town north of Naples

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Arrests part of large police operation aimed at tackling organized crime